Changes of hormons (T3, T4 and cortisol) and ions (Na+, Cl-, K+) during smoltification in Salmo trutta caspius Kessler 1877

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Abstract

Salmo trutta caspius is an important and economic fish in the Caspian Sea has several
morphological and physiological changes during smoltification. In this study, Hormonal (T3,
T4 & Cortisol) and ionic (Na+, Cl- & K+) changes in the serum were determined during the
period of smoltification in 5, 10, 15 & 20g of hatchery reared salmo trutta caspius in different
seasons (spring, summer, autumn & winter). Hormones were measured by Eliza and Radio
Immuno Assay, Na+ and K+ using flame photometer, Cl- by colorimeter. T3 and T4 were quite
high in spring, especially in the juvenile of 20g. Cortisol was quite low in spring and summer
in all of weight groups. Ionic changes showed no significant differences with weight, but it
was significantly different among seasons. This result suggests that analyzing the plasma
thyroid hormones and ionic provide useful information about the optimal time of transferring
Caspian Sea trout from fresh water to sea water. It is concluded that the juvenile fish of 20g
shows a better smoltification process in the spring.

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Iranian Scientific Fisheries Journal
Volume 21, Issue 3 - Serial Number 80
November and December 2012
Pages 119-128

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